

HYDRAULICS. 195 



the pump-barrel which the plunger moves up and 

 down in. 



On the top of the pipe O is a close air-vessel 

 P. When the water is forced up above the spout 

 O, it compresses the air in the vessel P; and this 

 air, by the force of its spring acting on the water, 

 causes the water to run off by the spout O, in a 

 constant and (very nearly) equal stream. 



Whatever the height of the spout O is above 

 the surface of the w T ell, the top S, of the pipe C, 

 must not be 32 feet above that surface ; because if 

 that pipe could be entirely exhausted of air, the 

 pressure of the atmosphere in the well would not 

 force the water up the pipe to a greater height 

 than 32 feet : and if S be within 24 feet of the 

 surface of the well, the pump will be so much the 

 better. 



The hair-rope machine for raising water was in- 

 vented by Sieur Vera. 



A (Fig. 8.) is a wheel four feet over, having an 

 axis and a winch : C C, a hair-rope, near one inch 

 diameter: D, a reservoir to collect the water: E, a 

 spout to convey the water from the reservoir: G, 

 the surface of the water in the well: I, a pulley 

 under which the rope runs, in order to keep it 

 tight. 



When the handle is turned about with a con- 

 siderable velocity, the water which adheres to the 

 rope (in wells of no great depth), is very con- 

 siderable; the rope thus passes through the tubes 

 in D, which, being five or six inches higher than 

 the bottom of the reservoir, hinders the water 

 from returning back into the well, and is conveyed 

 in a continual stream through the spout E. Some 

 of the above engines have raised a greater quantity 

 of water, than any person unskilful in hydraulics 



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